Volume overload due to left-to-right shunting in patients with atrial septal defect type secundum causes pulmonary vascular disease over a long period of time. Pulmonary vascular resistance can be assessed non-invasively using bicycle stress echocardiography. By measuring cardiac output and pulmonary artery pressures at different stages of exercise, a pressure-output plot can be obtained. The slope of the pressure-output plot reflects pulmonary vascular resistance. In patients undergoing ASD repair after the age of 40 years, pulmonary vascular resistance was higher when compared to age-matched controls, indicating the presence of mild pulmonary vascular disease. Bosentan has been shown to decrease pulmonary vascular resistance.

The investigators hypothesize that in patients with an ASD type secundum, who underwent ASD repair after the age of 40 years, administration of bosentan decreases pulmonary vascular resistance as assessed by bicycle stress echocardiography.

Signed informed consent by patient prior to initiation of any study-mandated procedure.

Male or female patients > 40 years with atrial septal defect type secundum and > 40 years of age at the time of repair

Women of childbearing potential must have a negative pre-treatment pregnancy test and must use a reliable method of contraception during study treatment and for at least 3 months after study treatment termination.

Women not of childbearing potential are defined as postmenopausal (amenorrhea for at least 1 year), or documented surgically or naturally sterile.

Exclusion Criteria:

Pregnancy or lactation

Women of child-bearing age who are sexually active without practising reliable methods of contraception

Any disease or impairment that, in the opinion of the investigator, excludes a subject from participation

Substance abuse (alcohol, medicines, drugs)

Other medical, psychological or social circumstances that would adversely affect a patient's ability to participate adequately in the study or increase the risk to the patient or others in the case of participation

Insufficient compliance

Subjects who are not able to perform cardiopulmonary exercise testing

ASD repair < 6 months before inclusion

PAH of any aetiology other than the one specified in the inclusion criteria

Impairment of organic function (renal, hepatic)

Arterial hypotension (systolic blood pressure < 85 mmHg)

Anaemia (Hb< 10 g/dl)

Decompensated symptomatic polycythemia

Thrombocytopenia (< 50000/µl)

Significant valvular diseases, other than tricuspid or pulmonary regurgitation

Chronic lung disease or total lung capacity < 80% of predicted value

History of significant pulmonary embolism

Other relevant diseases (HIV infection, Hep B/C infection)

Subjects with known intolerance to bosentan or their constituents

Prohibited medication: any medication listed below which has not been discontinued at least 30 days prior to screening

Unspecified or other significant medication (glyburide or immunosuppression)

Medication that is not compatible with bosentan or that interferes with its metabolism (inhibitors of CYP2C9 or CYP3A4) or that, in the investigator's opinion, may interfere with bosentan treatment.

Contacts and Locations

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To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT01218607